| 摘要 |
<p>A linear detector (61) for use in a coarse positioning servo system of an optical system. The linear detector produces an error signal having an amplitude linearly proportional to the distance that a relatively narrow strip of light energy (63) falls on a collection surface (62) of the detector as measured relative to a fixed reference point on said collection surface. Two reference signals (65, 66) are derived from circuitry associated with the collection surface. A frist reference signal (65) has an amplitude proportional to the intensity of the focussed light energy and the location that said light energy falls on the collection surface relative to a first reference point. A second reference signal (66) has an amplitude proportional to the intensity of the focussed light energy and the location that said light energy falls on the collection surface relative to a second reference point. The sum and difference of the amplitudes of the first and second reference signals are derived to produce sum and different signals, respectively. The difference signal is divided by the sum signal to produce the desired error signal (67), which error signal has an amplitude that is substantially independent of the intensity of the focused light energy. </p> |
